Generally, in the pneumatic tire provided with a lot of blocks in the tread surface, there is a tendency that a heel and toe wear is generated by a difference in a wear amount between a trailing side and a leading side of the block, due to a deformation at a time of rolling, and the heel and toe wear is particularly remarkable in the shoulder block arranged in the shoulder portion.
Conventionally, for the purpose of reducing the heel and toe wear, there has been employed a method of lifting up the bottom of the slits (the transverse grooves) sectionalizing the shoulder blocks so as to make the slit shallow, and enhancing a rigidity of the blocks so as to reduce a deformation. However, in this method, since a decay time of the slit is anticipated by the wear of the tread portion, there is generated a problem for maintaining a traction performance and a drainage performance.
On the contrary, the following Patent Documents 1 and 2 describe a method of forming a peculiar shape in which an angle of a slit wall surface (a groove wall angle) with respect to a tire diametrical direction of the block is different from each other between a trailing side and a leading side, and controlling a deforming degree of the block or the like in such a manner as to be advantageous to a heel and toe wear resistance. However, an effect of improving the heel and toe wear resistance according to the method mentioned above appears in the early stage of the wear, however, tends to fade with the reduction of the peculiar shape in the slit wall surface of the block in the stage that the wear of the tread portion makes progress.    Patent Document 1: Japanese Unexamined Patent Publication No. 2006-137230    Patent Document 2: Japanese Unexamined Patent Publication No. 2004-58889